Spatiotemporal Boundary Formation (SBF) is the formation of illusory boundaries and completed shapes from spatially separated, local element transformations (Shipley & Kellman, 1994, 1996). We tested a computational model of SBF based on a proof that local edge orientation and global motion could be derived from three non-collinear, sequential, local events (such as element disappearance, color change, local motion, or local orientation change). We hypothesized that due to noise in registration of key inputs, the ideal model would exceed human performance. In three experiments, we measured orientation discrimination thresholds for edges defined by SBF as a function of element quantity (Exp. 1), element density (Exp. 2) and rate of element change (Exp. 3). In all three experiments, black circular elements on a white background disappeared whenever they came into contact with an illusory edge and reappeared when the edge moved beyond. Human performance was inferior to the ideal model. We developed a more realistic model by incorporating two kinds of noise: noise in registration of the relative positions of the elements, and noise in the velocity of the virtual object. Estimates were obtained by fitting the model to data from one condition. The improved model predicted average thresholds with high precision in the first two experiments and not well in the third. We suspect that this is due to minor, but important differences in display generation across the experiments. The model produced estimates of edge orientation from the positions and rates of transformation of elements in the display for each trial. The model’s threshold estimates were then derived by submitting these results to the same staircase procedure used for human observers. These results offer a plausible account of how local element changes are used by the visual system to produce object boundaries, shape and global motion in SBF.